Liftoff to Learning: All Systems Go! .

VideoTitle: All Systems Go!Video Length: 33:34
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Description: This program discusses the reasons for and demonstrates
some of the physiologic changes that occur in the human body while
in the microgravity environment. This video may be shown in its entirety
or in segments.

The STS-40 Spacelab Life Sciences-1 (SLS-1) mission conducted extensive
research on six human body systems to better understand how humans will
be able to live and work for extended periods of time in space.

The experiments on the SLS-1 mission were aimed at trying to answer many
important questions about the functioning of the human body in microgravity
and its re-adaptation upon return to the normal gravity environment on
Earth. How does spaceflight influence the heart and circulatory system,
metabolic processes, muscles and bones, and the cells? Will the human
body maintain its physical and chemical equilibrium during long space
missions? If certain body adaptations to microgravity are undesirable,
how can those adaptations be prevented or controlled? When an astronaut
returns to Earth, how does the body readjust to gravity?

Spacelab is an international resource for scientific investigations in
space. Built by the European Space Agency for NASA, Spacelab is mounted
in the Space Shuttle's payload bay. For SLS-1, the Spacelab long module
configuration (seven meters long by five meters wide) was used for the
mission. It is a pressurized cylindrical module that is connected to the
airlock in the orbiter's middeck by a tunnel. The inside of Spacelab's
interior was arranged with two long racks of scientific apparatus and
support equipment that stretched along the walls on either side. Larger
pieces of equipment, such as a bicycle ergometer and a device that measures
body mass, were placed in the center aisle.

The scientific investigations conducted on SLS-1 explored some of the
limits, adaptations, and capabilities of the following human body systems
in microgravity: cardiovascular, cardiopulmonary, neurovestibular, musculoskeletal,
renal-endocrine, and blood and immune.

Although the data analysis-from the SLS-1 mission is continuing, researchers
have pieced together some of the changes that take place in living organisms
and living cells during exposure to microgravity. Human, plant, and animal
cells exposed to the microgravity of space for only a few days show changes
in function and structure. The data suggest that alterations in cell metabolism,
immune cell function, cell division, and cell attachment have occurred in
space. Scientists have reported that after nine days in space, human immune
cells failed to differentiate into mature effector cells. The results of
investigations into how the stress of space flight can alter normal metabolic
activities and important aspects of immune cell function may indicate the
body's inability to produce mature and fully differentiated cells in space.
This may lead to health problems on long-term spaceflights, including impaired
healing abilities and increased risk of infection.

Studies on rat bone cells revealed a significant number of floating, dead
bone forming cells. Bone cells die if they are unsuccessful in attaching
themselves to something. This finding could be significant since many biological
processes, both in single cells and in multi-celled organisms, depend on
cell attachment and the recognition processes. The finding suggests that
gravity clues may be required to show the cells where to attach themselves.
Furthermore, studies of rat bone cells also revealed that healthy cells
showed no signs of producing minerals. It may be that bone cells do not
need to produce minerals to support themselves in a microgravity environment.

Similar studies of mouse bone cells developed in space and of those developed
on the ground revealed similar changes in attachment properties in microgravity.
Microscopic examination of the surfaces of flight cells revealed that they
were smoother than cells used in the ground-based control experiment. This
finding indicated that matrix production or secretion is altered in microgravity.
Matrix forms the basic structure of bone.

Plant cell studies also revealed unusual responses to microgravity. Data
collected indicated that cells in the roots of plants subjected to spaceflight
undergo major changes in their cell division profile, even after as few
as four days in space. One plant studied, Haplopappus gracilis, has
only four chromosomes. Overall root production in this plant was significantly
faster under spaceflight conditions than in ground control studies. Furthermore,
changes in chromosomes were found in up to one-third of the cells that flew
in space.

Scientists have reported dramatic changes associated with space travel in
some of the human body systems, with a resiliency in others, all of which
may affect long stays in space and medical research on Earth. These results
point to the need for a long term laboratory in space to complement Earth-based
laboratory research. Key findings from the SLS-1 mission for three of the
major body systems studied (cardiovascular, musculoskeletal, and neurovestibular)
revealed important changes that take place in the human body in microgravity.

Cardiovascular
Space travel presents a drastic change in working conditions to the heart
and lungs. Often, astronauts who have just returned from space have difficulty
maintaining normal blood pressure and blood flow when standing. One SLS-1
experiment used a catheter inserted preflight into an arm vein of an astronaut
and later moved nearer to the heart. This catheter had a sensor attached
which measured the blood pressure closest to the heart. The experiment showed
that the astronaut experienced a much more rapid fall in central venous
blood pressure than was predicted.

In another area of cardiovascular research, it was found that exposure to
space impairs an astronaut's pressure-regulating reflexes, called baroreflexes.
A closely-fitting neck collar (similar to a whip-lash collar) was used on
astronauts during the SLS-1 mission to test and record two blood pressure
sensing areas located in the neck.

By the eighth day of flight, astronauts had significantly faster resting
heart rates, less maximum change of heart rate per unit of neck pressure
change, and a smaller range of heart rate responses. The changes that developed
were large, statistically significant, and occurred in all astronauts studied.
These results validated findings obtained on Earth by studying subjects
after prolonged bed rest. This validation can lead to important studies
in clinical medicine and provide insights into medical problems here on
Earth.

Nervous System
The results of another SLS-1 experiment show clear evidence that the number
of structures (synapses) used to communicate between the cells of the inner
ear's gravity detecting organ and the central nervous system increases during
spaceflight, but the size of these structures does not increase. Therefore,
these systems should be able to adapt to the differing gravitational environments
of space, the Moon, and Mars. Further research in this area should also
shed light on the broader topics of memory and learning in neural tissue
and on clinical diseases of the inner ear.

Muscles
During spaceflight,there is a significant and dramatic reduction in the
size of all muscles needed for standing and moving. Furthermore, it seems
that there is a reduced capacity of muscles to burn fat for energy production.
Studies have also verified that muscles that support the body when we walk
on Earth change their nature in space because they are not needed. Taken
together, these findings suggest that properties of the skeletal muscle
system, the largest organ system of the body, are greatly altered during
spaceflight.

Additional Findings

As researchers continue to analyze the data collected through the experiments
of the Spacelab Life Sciences-1 mission, reports of the findings will be
made public through professional journals. Refer to the reference list for
sources of additional information.

Procedure
Demonstrate one of the changes that takes place in the human body in microgravity
by having students measure their height immediately after rising in the
morning and just before going to bed at night. People are measurably taller
in the morning than they are in the evening. During bed rest, the disks
that separate the vertebrae in the spinal column expand slightly. This increases
the total body height by a centimeter or more. By evening, the disks have
been compacted, producing a shorter body height. During exposure to microgravity,
the spine expands and doesn't contract until to return to Earth.

Procedure
Measure the circumference of the mid-calf of several volunteer students
while they are standing. Carefully mark the placement of the tape measure
with the marker pen. Record the measurement. Lay each student down on the
table in turn and elevate one end of the table by placing the legs on the
wood blocks. The student should be in a head-down position. Ask the student
to describe the sensations felt, especially in the head and upper body.
After five minutes of "bed rest," measure the circumference of
the calf again in the exact place as before. Record the measurement. Is
there a difference in the two measurements? What might cause these differences?

Note: While standing on Earth, gravity tries to pull blood and other body
fluids to the feet. Without the pumping action of the legs during movement,
humans standing still for long periods tend to black out. In Earth orbit,
the local effects of gravity are counteracted, but the pumping actions of
the legs continue. This leads to an upper body fluid shift that creates
a puffy look in the face and neck and a thinning of the calf ("chicken
legs"). Bed rest can simulate this effect.

Procedure
Measure the pulse rate (in beats per minute) of a volunteer student standing
at rest. Record the rate. Give the volunteer the hand weights and have the
student exercise vigorously with them for two to four minutes. Again, measure
and record the heart rate. When the heart rate has returned to the rate
at rest, place the student on the table. Elevate the end of the table under
the student's feet. After five minutes of "bed rest" with the
feet elevated, measure the volunteer's heart rate. Again, give the student
the hand weights and have the student exercise vigorously for two to four
minutes while still lying down. Measure and record the heart rate after
exercise. Calculate the cardiac output for each measure. The cardiac output
in milliliters per minute equals the stroke volume (ml/beat) times the heart
rate (beats per minute).

Cardiac Output = Stroke Volume x Heart Rate

Assume that the standing stroke volume is about 75 ml/beat. During bed rest
and in microgravity, the stroke volume increases to about 95 ml/beat. Was
there a difference in cardiac output before and after exercise while standing?
During bed rest? Compare standing cardiac output with bed rest (microgravity)
output. Is there a difference? Why or why not?

Note: This activity and the proceeding one can be combined into a single
study.